This invention relates to master cylinders that are used with vehicle braking systems and, more particularly, to housings for master cylinders.
To increase safety, most modern automobile braking systems are comprised of two hydraulic circuits, with two wheels connected to each circuit. If a fluid leak occurs in one circuit, only two of the four wheels of the vehicle will lose their braking ability, enabling the vehicle to stop when the driver presses on the brake pedal.
A key component of the dual-circuit hydraulic braking system is the master cylinder. The master cylinder supplies hydraulic pressure to both circuits of the vehicle, and is comprised of two pistons within a common master cylinder housing. When the driver presses the brake pedal, a linkage coupled to the brake pedal pushes on a primary piston of the master cylinder. Pressure builds in the master cylinder, and in a first braking circuit coupled to the master cylinder, as the brake pedal is depressed. Hydraulic pressure also builds between the primary piston and a secondary piston, displacing the secondary piston and causing the secondary piston to compress fluid in a second braking circuit. The hydraulic pressure in both braking circuits is transmitted to brake devices on each wheel of the vehicle, causing the brake devices to engage a rotating portion of the wheels. The resulting friction between the brake devices and the rotating portion of the wheels acts to slow or stop the vehicle.
Proper operation of the braking system depends on the integrity of the hydraulic system. The master cylinder must be capable of generating several hundred pounds per square inch of hydraulic fluid pressure and the entire braking system must maintain this pressure without leaking. Thus, a master cylinder housing is preferably made of robust, high-strength materials. However, there is a conflicting design constraint wherein it is desirable to make the master cylinder housing as light as possible to keep the vehicle's weight down. Yet another conflicting design constraint is a desire to produce an inexpensive master cylinder housing to keep down the manufacturing cost of the vehicle.
Accordingly, there is a need for a relatively lightweight, robust master cylinder housing that is relatively inexpensive to produce.